Bleeding that occurs during pregnancy and appears at about the time a woman would normally have her menstrual period is called decidual bleeding.

It is not a very common occurrence and it usually doesn't last longer than the first few months of pregnancy. It can be similar to menstrual bleeding and can actually cause a woman to think she isn't pregnant when in fact, she is.

This type of bleeding is the result of a disturbance in the fluctuation of hormones that normally occurs during pregnancy. When the pregnancy hormones are not rising and falling as they should, it can cause some shedding of the uterine lining in spite of pregnancy.

Decidual bleeding is most common in the very early stages of pregnancy, before the establishment of the placenta. However, there are some women who do continue to have decidual bleeding throughout their pregnancies.

Decidual bleeding should be checked by your doctor

Although decidual bleeding is not considered dangerous to either the mother or baby, it is still a good idea to inform the doctor of any bleeding that may occur during pregnancy. Sometimes bleeding can be caused by a more serious condition, so reporting it to the doctor is the best action to take.

Bleeding during pregnancy can occur for a variety of reasons. Learn more about it in the article about menstruation and pregnancy in this section.